Aveeno Skin Relief Body Wash Versus Cetaphil Ultra Gentle Body Wash

Your skin makes glycerin on its own (mostly from sebaceous oil breakdown) and shuttles it to your outermost layer of skin, or your epidermis, via aquaporin-3.

Aquaporin-3 is a transporter that is essential for normal skin hydration, elasticity, and repair. Interestingly, mice lacking in AQP3 have dry and less elastic skin that can be fully corrected with glycerin.

This ingredient is non-irritating, plays well with almost every ingredient, and works across all skin types. Typical use is anywhere between 3-10% but can go up to 79% in some leave-on products.

Just know very high concentrations (>40%) can feel tacky in low humidity.

Glycerin is the name for this ingredient in American English. British English uses Glycerol/Glycerine.

This ingredient is considered safe at present practices of use and concentration and repeated insult patch test with 50% Glycol Distearate on 125 subjects found no evidence of skin irritation, hypersensitivity, or acute toxicity.

Typical use concentrations range from 0.1-10%.

Because it's an ester of stearic acid, it falls into the range that Malassezia likes to metabolize. This ingredient may not be fungal acne safe.

A 2012 assessment found this ingredient is used in leave-on products at up to 21%, which is at the very high end for the category; most cosmetic use is far lower and typically in the single digits.

A true allergy to Laureth-4 is rare; similar alcohol ethoxylates tested negative for skin sensitization in undiluted guinea pig studies, and related compounds were non-sensitizing in Magnusson-Kligman maximization tests.

There is one caveat for this whole ingredient family: ethoxylated surfactants slowly oxidize when exposed to air, and it's the oxidation products, not the fresh material, that act as sensitizers. This is mostly a formulation and shelf life issue.

Dr. James Fulton's rabbit ear test from the 1980's scored this ingredient as a 5 on the comedogenic scale. Fulton himself described the rabbit ear as not an ideal model and the tests used undiluted ingredients on rabbit ears, which are more reactive than human facial skin.

Dr. Draelos later used a human assay on finished cosmetic products and found that products built with so-called comedogenic ingredients are not necessarily comedogenic themselves.

This ingredient can be potentially pore clogging if it appears high in the ingredient list of a leave-on product.

The fungal acne picture is actually reassuring: Malassezia uses fatty acids from its surroundings (C11-24). This ingredient has nothing for the Malassezia yeast to use since it is an alcohol and not an acid.

Supporting this, closely related ethoxylated alcohol detergents like Ceteth-20 get used in Malassezia lab work as neutral carriers to disperse a separately added fatty acid (not as the food source itself).

For haircare friends: this ingredient is not a silicone.

Sodium benzoate works as a preservative by inhibiting the growth of bacteria inside of cells. It prevents the cell from fermenting a type of sugar using an enzyme called phosphofructokinase.

It is the salt of benzoic acid. Foods containing sodium benzoate include soda, salad dressings, condiments, fruit juices, wines, and snack foods.

Studies for using ascorbic acid and sodium benzoate in cosmetics are lacking, especially in skincare routines with multiple steps.

We always recommend speaking with a professional, such as a dermatologist, if you have any concerns.

Your skin has a natural pH and acid mantle. This acid mantle helps prevent harmful bacteria from breaking through. The acid mantle also helps keep your skin hydrated.

"Alkaline" refers to a high pH level. A low pH level would be considered acidic.

Sodium Laureth Sulfate is a type of sulfate. It can be drying. We recommend speaking with a professional about using this ingredient if you have concerns.

You'll also recognize water as that liquid we all need to stay alive. If you see this, drink a glass of water. Remember to stay hydrated!